1. Field of the Invention
The present invention relates to a dustproof bearing device for a motor. In particular, the present invention relates to a dustproof bearing device that prevents entrance of dust and impurities into the bearing of the motor and that prevents loss of lubricating oil of the bearing.
2. Description of the Related Art
FIGS. 7 and 8 of the drawings illustrate a conventional bearing structure comprising an axle tube 90, an upper cap 91 tightly fitted in an upper end of the axle tube 90 and having a hole 911, a rotor having a shaft 92 extending through the hole 911 of the upper cap 91, and a connecting member 93 for retaining the upper cap 91 on the shaft 92. The connecting member 93 includes an annular wall 931 that extends beyond the hole 911 of the upper cap 91 and abuts against a shaft base 921 of the rotor. An oily bearing 94 is mounted around the shaft 92 and located below the connecting member 93. The oily bearing 94 is mounted in the hole 911 of the axle tube 90 in a non-tight engaging relationship. A lower cap 95 is mounted to a lower end of the axle tube 90, thereby limiting the oily bearing 94 between the upper cap 91 and the lower cap 95 for rotatably holding the shaft 92 of the rotor.
As illustrated in FIG. 8, since gaps exist between the annular wall 931 of the connecting member 93 and the hole 911 of the upper cap 91 and between the connecting member 93 and an inner periphery of the upper cap 91, dust and impurities are apt to enter the bearing 94 in the axle tube 90 through the gaps and thus accumulate between the bearing 94 and the shaft 92 of the rotor. As a result, the bearing 94 and the shaft 92 of the rotor are worn out rapidly.
FIG. 9 illustrates a heat-dissipating fan having a conventional dustproof structure. The fan includes an impeller 8 having a shaft 82 extending from an end wall thereof and a magnet 83 attached to a peripheral wall thereof. At least one set of concentrically arranged ribs 84 is provided on an inner face 81 of the end wall of the impeller 8. The ribs 84 are located at a level adjacent to an upper pole plate 86 of a stator 85, thereby forming a curved small gap between the ribs 84 and the upper pole plate 86. An axle tube 87 extends through the stator 85 and includes an upper end 870 close to the inner face 81 of the end wall of the impeller 8, thereby forming a curved small gap between the upper end 870 of the axle tube 87 and the inner face 81 of the end wall of the impeller 8. The configuration of the ribs 84 and the upper end 870 of the axle tube 87 increase the length of the path through which air flows, and the curved small gaps prevent dust from entering the shaft 82 when the impeller 8 turns. However, although it is difficult for the dust to enter the shaft 82, the dust may still enter the gap between the shaft 82 and the bearing 88 if the dust enters the axle tube 87. Further, the dustproof structure fails to prevent loss of the lubricating oil in the bearing 88.
An object of the present invention is to provide a dustproof bearing device for a motor, wherein dust and impurities are reliably prevented from entering the bearing, thereby lengthening the life of the bearing.
Another object of the present invention is to provide a dustproof bearing device for a motor, wherein loss of the lubricating oil contained in the oily bearing is prevented, thereby lengthening the life of the bearing.
A motor in accordance with the present invention comprises an axle tube, a rotor, and a member. The axle tube includes a hole, and a stator is mounted to an outer periphery of the axle tube. The rotor includes an end wall having a shaft base from which a shaft extends. An annular wall extends from an inner face of the shaft base and surrounds the shaft. The member is mounted in the hole of the axle tube and rotatably receives the shaft of the rotor. The member includes a reduced section, forming a gap between the reduced section of the member and the axle tube. The annular wall extends into the gap between the reduced section of the member and the axle tube.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.